I went to my local bss and the lady recommended this product for dark knuckles. Apparently it acts as a peel for the skin. Am going to try it out and give my reviews, pics included. My knuckles aren't dark necessarily but they could do better. I am hoping I don't mess up my hands. If anyone has used this, please do contribute.
Here is a picture;
Main ingredients; fruit acids, high percentage of salicylic acid. On the label it says to use on only elbows, knees, knuckles not the face. Product causes callosity of the skin.